A,B,C,D,E,F,G是初中化学常见的物质,其中A,D,G是单质,其它是化合

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问题:

A,B,C,D,E,F,G是初中化学常见的物质,其中A,D,G是单质,其它是化合物,C是天然气的主要成分,F的水溶液呈蓝色,G是目前产量最大的金属,图中“-”表示相连的物质两两之间可以发生反应,“→”表示由某一物质可制得另一物质(部分反应物、生成物及反应条件已略去).

(1)物质C的化学式为______.A物质的用途是______(任写一种)

(2)图中涉及复分解反应的化学方程式可能是______

(3)G在D中反应时的现象是______.

考点:物质的鉴别物质的推断
题型:问答题

中国企业发展网络经营还存在着一些不可忽视的制约因素,主要表现为()。

A.虚假广告宣传

B.无照网络经营

C.利用互联网贩私

D.合同诈骗

题型:问答题

起重机的安全工作寿命,主要取决于()不发生破坏的工作年限。

A.工作机构

B.机构的易损零部件

C.金属结构

D.电气元件

题型:问答题

水泥熟料矿物中水化速度最快的熟料是()

A.硅酸三钙

B.硅酸二钙

C.铝酸三钙

D.铁铝酸四钙

题型:问答题

下列不符合小脑幕切迹疝临床表现的是

A.头痛剧烈、呕吐频繁、烦躁不安
B.呼吸骤停、瞳孔无变化
C.病侧瞳孔先缩小,继之散大
D.散大瞳孔的对侧肢体运动障碍
E.进行性意识障碍

题型:问答题

A bite of a cookie containing peanuts could cause the airway to constrict fatally. Sharing a toy with another child who had earlier eaten a peanut butter and jelly sandwich could raise a case of hives. A peanut butter cup dropped in a Halloween bag could contaminate the rest of the treats, posing an unknown risk.

These are the scenarios that "make your bone marrow turn cold" according to L. Val Giddings, vice president for food and agriculture of the Biotechnology Industry Organization. Besides representing the policy interests of food biotech companies in Washington, D. C., Giddings is the father of a four-year-old boy with a severe peanut allergy. Peanuts are only one of the most allergenic foods; estimates of the number of people who experience a reaction to the beans hover around 2 percent of the population.

Giddings says that peanuts are only one of several foods that biotechnologists are altering genetically in an attempt to eliminate the proteins that do great harm to some people’s immune systems. Although soy allergies do not usually cause life-threatening reactions, the scientists are also targeting soybeans, which can be found in two thirds of all manufactured food, making the supermarket a minefield for people allergic to soy. Biotechnologists are focusing on wheat, too, and might soon expand their research to the rest of the "big eight" allergy-inducing foods: tree nuts, milk, eggs, shellfish and fish.

Last September, for example, Anthony J. Kinney, a crop genetics researcher at DuPont Experimental Station in Wilmington, Del., and his colleagues reported using a technique called RNA interference (RNAi) to silence the genes that encode p34, a protein responsible for causing 65 percent of all soybean allergies. RNAi exploits the mechanism that cells use to protect themselves against foreign genetic material; it causes a cell to destroy RNA transcribed from a given gene, effectively turning off the gene.

Whether the public will accept food genetically modified to be low-allergen is still unknown. Courtney Chabot Dreyer, a spokesperson for Pioneer Hi-Bred International, a subsidiary of DuPont, says that the company will conduct studies to determine whether a promising market exists for low allergen soy before developing the seeds for sale to farmers. She estimates that Pioneer Hi-Bred is seven years away from commercializing the altered soybeans.

Doug Gurian-Sherman, scientific director of the biotechnology project at the Center for Science in the Public Interest—a group that has advocated enhanced Food and Drug Administration oversight for genetically modified foods—comments that his organization would not oppose low-allergen foods if they prove to be safe. But he wonders about "identity preservation" a term used in the food industry to describe the deliberate separation of genetically engineered and no nengineered products. A batch of nonengineered peanuts or soybeans might contaminate machinery reserved for low-allergen versions, he suggests, reducing the benefit of the gene-altered food. Such issues of identity preservation could make low-allergen genetically modified foods too costly to produce, Chabot Dreyer admits. But, she says, "it’s still too early to see if that’s true. \

What can be inferred about genetically modified foods from the text()

A. People do not accept any genetically modified foods

B. All genetically modified foods will be of benefit to people’s health

C. Genetically modified foods still have a long way to go

D. Genetically modified foods will soon be sold in supermarkets

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